According to a study presented at the American Thoracic Society International Conference, people who smoke marijuana–even heavy, long-term marijuana users–do not appear to be at increased risk of developing lung cancer.
The study also found that marijuana smoking did not appear to increase the risk of head and neck cancers, such as cancer of the tongue, mouth, throat, or esophagus.
The researchers were surprised with the findings. “We expected that we would find that a history of heavy marijuana use–more than 500-1,000 uses–would increase the risk of cancer from several years to decades after exposure to marijuana,” said the senior researcher, Donald Tashkin, M.D., Professor of Medicine at the David Geffen School of Medicine at UCLA in Los Angeles.
The study found that 80 percent of lung cancer patients and 70 percent of patients with head and neck cancer had smoked tobacco, while only about half of patients with both types of cancer smoked marijuana.
Dr. Tashkin said the next step is to study the DNA samples of the subjects, to see whether there are some heavy marijuana users who may be at increased risk of developing cancer if they have a genetic susceptibility for cancer.
American Thoracic Society (2006, May 26)